set function for lists on numbers, sometimes sorts elements from smallest to largest, and sometimes not
to find this bug, sometimes you need to display the result several times
example code:
def tupla():
    import random
    ilosc = random.randint(0,49)
    n=0
    lista=[]
    i=0
    while True:
        n = random.randint(1,100)
        lista.append(n)
        i=i+1
        if i==ilosc-1:
            break
    lista = set(lista)
    list(lista)
    print(lista)

This is expected behavior. A set has no defined order. If you convert a set to a list, and you want some specific order, you'll need to sort it yourself.